Oelrichs: Fairburn Agate & Jasper Rockhounding in Fall River County, South Dakota

Plan your visit

Generally open to casual rockhounding

County

Fall River County

State

South Dakota

Coordinates

43.12561, -103.16692

Coordinates are approximate. Confirm the exact ground in the RockHoundR app, where land overlays show which agency manages the area.

Land & collecting status

Generally open to casual rockhounding

Most public-tagged spots sit on BLM, U.S. Forest Service, or other federal land where reasonable hand collecting of common rocks and minerals is allowed. Confirm posted rules and active mining claims before you dig.

Access note: This Fall River County locality lies on Buffalo Gap National Grassland near the US-18 and US-385 corridor, where USFS rules permit personal-use surface collecting of rocks and agates without a permit. Important boundary note: the Pine Ridge Reservation begins just east in Oglala Lakota County, and collecting there requires tribal permission, so collectors should keep to the Fall River County grassland west of the reservation line and off posted private land.

Public-land rules vary by agency, season, and field office. The RockHoundR app pulls live BLM, USFS, NPS, and tribal overlays so you can see exactly which agency manages the ground at this spot.

Best time to visit Oelrichs

Comfortable months (45 to 90°F highs)

Best months: March to November. Typical highs run 89°F in midsummer and 36°F in midwinter, with winter lows near 13°F.

Climate normals: NOAA 1991-2020 monthlies, OELRICHS station (6 mi away).

Geology at Oelrichs

This spot sits on Pierre Shale, mapped as shale and bentonite that formed roughly 100 to 66 million years ago. Sedimentary beds like these are the typical host for petrified and silicified wood, which weathers out as durable float on slopes and in washes.

Mapped unit

Pierre Shale

Age

100–66 Ma (Late Cretaceous)

Rock types

shale and bentonite

Elevation

3,360 ft

Geologic mapping via Macrostrat and the underlying state geological survey maps (CC BY 4.0). Bedrock at the surface can vary within a mapped unit.

Sources & verification

Spot details combine the public RockHoundR location dataset, normalized mineral labels, agency land-status checks in the app, and community submissions. Coordinates are approximate until verified in the field.

• BLM Montana-Dakotas rockhounding rules
• Buffalo Gap National Grassland
• South Dakota Geological Survey
• Community submissions reviewed against published agency rules